Effects Of Wave Height Research Articles

An experimental study of a rectangular floating breakwater with flexible curtains as wave-dissipating components

In this study, the flexible curtains are attached to the bottom of a rectangular floating breakwater as wave-dissipating components. Through a comprehensive experimental investigation, the wave attenuation, motion responses, and mooring forces of the proposed floating breakwater are examined, with a particular focus on the effects of wave height and the hanging length and porosity of the flexible curtain. Meanwhile, comparative analyses are conducted with the stand-alone rectangular floating breakwater and with attaching one rigid slotted barrier. Our experimental results indicate that one underhanging flexible curtain can augment wave attenuation across all tested wave conditions, which is comparable to the rigid slotted barrier. Furthermore, attaching two flexible curtains contributes to a more significant enhancement for harbor or coastal protection, especially against long waves. This can be attributed to the buffer function of flexible curtains, and the increased added mass induced by the water body confined between them, which increases the natural period of floating breakwaters. Furthermore, the attachment of the flexible curtains significantly suppresses the motion responses of the breakwater, which can alleviate the undesirable strong mooring forces. In general, increasing the length or decreasing the porosity of flexible curtains leads to similar trends in the performance of floating breakwaters. The flexible curtains have been proven to be effective wave-dissipating components for rectangular floating breakwaters.

The influence of toe geometry on toe armour stability for conventional rubble mound breakwaters

Rubble mound breakwaters have toe structures that provide support to the armour layer and prevent damage to the structure from scouring. In this way, toe failure may be regarded as one of the primary failure modes of rubble mound breakwaters. Several formulae have been proposed for toe stability with conflicting results owing to the neglect of factors such as storm duration and armour layer slope. In the present study, a statically stable rubble mound with rock armoured toe was tested under irregular waves. The effects of wave height, wave period, armour layer slope, water height in front of the structure, water height above the toe, and toe width on the hydraulic stability of a toe structure are investigated. Toe width was found to be ineffective on toe stability, while the relative depth was found as an effective parameter for the toe stability. Greater toe damage was observed by increasing wave height and storm duration. The results highlighted the necessity for a new stability number involving the type of wave breaker on the armour slope with a critical Iribarren value of 4.1. Based on the data from the present study and the findings of another study, new formulae have been developed for estimating toe damage in rubble mound breakwaters. Evaluating the proposed formula using other researchers’ data and formulae highlighted its strengths.

Numerical investigation of cylinders’ motion trajectory and landing positions in regular waves

During the underwater motion of structures, random effect of waves and currents can lead to sudden changes in its hydrodynamic characteristics, the sudden changes in hydrodynamic characteristics and random effect of currents can further couple, seriously affecting its underwater motion mode affecting, so a targets' underwater motion situation model (TUMS) was proposed in this paper which can predict the targets' underwater motion trajectory envelope and the landing positions. Firstly, the influence of random factors such as wave, current, drag coefficient, and xt coefficient was considered based on the targets' three-dimensional (3-D) motion theory and a TUMS model was proposed. Secondly, the underwater motion trajectory of the cylinder is simulated using the TUMS model, and the numerical simulation results are compared with the experimental results which were in good agreement with experimental results. Thirdly, the effect of wave height and wave frequency on the cylinders' motion trajectory was discussed. Finally, the cylinders’ underwater motion trajectory envelope, landing position distribution, sinking bottom velocity distribution, and sinking bottom attitude distribution were calculated.

Experimental and numerical investigations on the solitary wave actions on a land-fixed OWC wave energy converter

The dynamic performance of a typical land-fixed oscillating water column (OWC) wave energy converter (WEC) under solitary waves (SW) is experimentally and numerically investigated. Both two-dimensional (2-D) and three-dimensional (3-D) numerical models are considered in the present study. The air orifices of the OWC chamber in 2-D and 3-D models are represented by a narrow rectangular opening and a circular opening, respectively, with the same opening ratio (i.e., the cross sectional area ratio between opening and the air chamber). It is found that the overflow of the orifice occurs when the wave height exceeds a threshold, which results in a larger wave force on the structure compared with that induced by the SW crest. The 2-D numerical model fails to predict the overflow phenomena due to the full submergence of the orifice. The overtopping and roof impacting phenomena are induced when the wave run-up exceeds the front wall height. A portion of the SW energy is released during this process. Hence, total wave forces are reduced. The effect of wave heights on force components exhibits different behaviors due to the coupling of air and water inside the chamber. Both the impacting force and overtopping discharge increase with incident wave heights.

Effect of wave height on harbor wall height in coastal waters using computational fluid dynamics

An essential aspect of the sustainable design of harbor walls is the determination of the design wave condition. It is predicted by utilizing severe wave conditions from the past 10 to 20 years. The tourism harbor in Central Maluku, Indonesia, is located where extreme wave conditions occur. Therefore, this research studies the wave height before and after constructing a harbor wall in the harbor area. The wave height was simulated using numerical modelling. The methodology was performed by using the coastal modelling software of the CFD model. The result shows the highest design wave height values of 0.5 m, 0.75 m, and 1 m in the direction from the southeast to harbor height 1 m. The simulation results show that the wave height is 1.5 m and the harbor height is still safe. Further study is needed to simulate the extension of harbor wall length to meet the criteria for wave height in the harbor basin.

Computer vision-based measurement of wave force on the rectangular structure

Measurement of the wave force acting on the structure is normally achieved by the traditional load cells. In this study, a non-contact computer vision (CV)-based method is proposed, which can conveniently acquire the wave pressure and force without installing pressure sensors or load cell mounted on the structure. Based on the velocity field measured by the Optical Flow technique, the pressure field is successfully computed by solving the Poisson pressure equation, and the wave force is further determined by integrating the pressure over the surfaces of the structure. The proposed method is verified by conducting a series of laboratory experiments of wave interacting with the rectangular structure. The accuracy of the method is validated by comparing with the results measured by pressure sensors. It indicates that the CV obtained pressure and wave forces generally agree well with the sensor measured results, including the time history of wave force and the peak wave force, and the reasons for the deviation and error are also discussed. The effects of wave height and wave period on the pressure field and wave force are studied, and it is found that the Keulegan–Carpenter number is an important parameter determining the peak wave force. Finally, the limitations existed in this method are noted, including the two-dimensional simplification and air bubble effects, which need to be addressed in the future.

A Parametric Study on Effect of Wave Height, Water Depth and Support Conditions on Behaviour of Offshore Jacket Structure

Fixed offshore jacket structures are constructed for facilitating oil/gas exploration and production. These structures and their foundations are designed to resist large vertical and lateral loads. Various factors including water depth, wave height and support conditions would affect the response of jacket structures. However, few studies have focused on understanding the response of offshore jacket structure due to variation in these factors. In this context, the present work evaluates response of typical X-braced, square base, 4-legged battered jacket structure using STAAD Pro. under combined vertical and lateral environmental loading. The variables included are water depth (60 m, 90 m and 120 m), wave height (5 m, 10 m and 15 m) and two foundation modelling approaches (viz., fixed at pile location and with defined pile stiffness). The connection between structure leg and pile location is modelled to simulate realistic connection. Deck loads, wind forces and current velocities are considered constant for this study. The wind and wave loads have been applied in parallel, perpendicular and diagonal directions with respect to jacket structure. The wave forces are calculated by Morrison’s equation. For obtaining pile stiffness, medium dense sand layer is considered as foundation soil. The increase in water depth and wave height results in corresponding linear increase in lateral deflection and support reactions, the effect of water depth being more prominent. Moreover, lateral and vertical deflection, shear force and bending moment in the legs, the axial forces in the lower tie beams and plan bracings, and support moments are observed to increase when pile locations are modelled with appropriate vertical, lateral and rotational stiffness instead of fixed support. The effect of water depth on member forces is higher as compared to wave height. The present work deliberates on the mechanisms/reasons to explain the observed results and contributes in direction of framing decision matrix for design optimization of jacket structures.

Effects of Forward Speed and Wave Height on the Seakeeping Performance of a Small Fishing Vessel

The effects of wave height and forward speed on the seakeeping performance of a small fishing vessel in irregular waves are evaluated using computational fluid dynamics (CFD). The wave height effect changed linearly for a forward speed in the head sea and beam sea. In the stationary state, the heave and roll motions attributed to the wave height appear nonlinearly. The effect of the speed showed a non-linear shape wherein the heave motion became larger with an increase in the forward speed in beam sea. The seakeeping performance of pitch motion is greatly improved at forward speed rather than in a stationary state. The seakeeping performance of the roll motion is more dangerous than the pitch motion, regardless of wave height and vessel speed. The mean roll period in irregular waves is obtained through this study, and it is longer than the natural roll period in still water. It is necessary to be careful as the probability of exceeding the limit is high and GM is decreased in transverse waves.

Experimental Investigation of the Dynamic Behavior of Submerged Floating Tunnels under Regular Wave Conditions

Submerged floating tunnels (SFTs) are an innovative traffic structure for transportation in deep and long-distance ocean environments. SFTs have the risk of being subjected to wave action in the complex ocean environment. Therefore, in order to ensure the safety and stability of SFTs during their service, the dynamic behavior of an SFT subjected to the action of waves is experimentally investigated in this study. Based on the wave–current flume, a physical scale-model experiment of an SFT for studying the dynamic behavior of an SFT subjected to regular waves interactions is deeply and thoroughly explored. The results show that the wave outputs from the wave-making system are verified to be reliable. The influence of major load parameters on the dynamic behavior of the SFT are deeply and thoroughly explored. The effects of wave height and wave period on acceleration, wave pressure, anchor cable force and displacement in an SFT are discussed. This experimental study has theoretical and practical significant for SFT design and safety.

An experimental study on the evolution of a submerged berm under the effects of regular waves in low-energy conditions

Reduced-scale mobile-bed flume tests are conducted on the evolution of a submerged berm under the effects of regular waves in low-energy conditions. Twenty-three flume tests are performed on a profile model of a submerged berm under different combinations of wave heights and wave periods. The profile shapes and water elevations along the profile are recorded during the tests. Comprehensive analyses are conducted on the profile evolution and the wave parameters along the profile of the submerged berm model. In all cases the crest of the submerged berm moves onshore and the profile shape become asymmetrical. Overall analyses are conducted on the evolution-related parameters such as the moving distance of the centroid ( D lc ), the change of skewness of the profile shape ( C sk ), the change of the crest elevation of the submerged berm ( C cl ) and the irregularity parameter of the profile shape ( K rms ). The effects of wave height and wave period on these parameters are discussed. An Empirical Orthogonal Function (EOF) analysis of the test results indicates two major evolution patterns of the submerged berm, onshore migration and onshore inclining of the crest, both of which are controlled by wave height. The velocity skewness, wave height and local water depth are the major factors that impact the onshore sediment transport under low energy conditions. No obvious connections can be found between acceleration skewness and sediment transport in this experimental study. However, large acceleration skewness would reduce the values of velocity skewness and impact the sediment transport indirectly. This paper proposes new insights on the morphodynamics of submerged berms under low-energy conditions and provide validation data for numerical models. • The evolution of a submerged berm under low-energy conditions are studied via a series of flume tests. • A general portrait on the feature of the evolution of a submerged berm under low energy conditions is given. • The effects of wave height and wave period on the shape-changing of the submerged berm are analyzed quantitatively. • Two major evolution patterns of the submerged berm in this case are onshore migration and onshore inclining of the crest. • The velocity skewness, wave height and local water depth dominate the onshore sediment transport under low energy conditions.

Wave forces on crown wall of rubble mound breakwater under swell waves

Crown walls are often used to reduce costs and increase the top of the rubble mound breakwater. Swell period waves often occur along the coast of South Asia, Africa, and South America and have attracted increasing attention. An experiment consisting of 744 tests was conducted to study the wave force on the crown wall under swell waves. Pressure transducers of 100 and 1000 Hz were arranged on the crown wall. Through comparison, the acquisition frequency of 1000 Hz can capture greater impact pressure than 100 Hz. The effects of wave height, water depth, wave period, slope, and berm width on the wave force were studied. Subsequently, experimental data were compared with the Pedersen, Martin, Nørgaard, and Code of China Design methods, and the applicability of these methods was analysed. A linear modified method was proposed to improve the original Pedersen, Martin, and Nørgaard methods. The results indicated that the improved methods have significantly smaller errors than those of the original methods. The improved Martin method was found to be the most effective in estimating horizontal force. The improved Nørgaard method was the most accurate for determining the uplifting force.

Experimental and Numerical Simulation of a Symmetrical Three-Cylinder Buoy

The wave resistance of a buoy is affected by the mode of anchorage and the buoy structure. Combining the structures and the mode of anchorage of the existing buoys, designing a buoy with significantly improved wave resistance is a major challenge for marine environment monitoring. This work carried out experimental and numerical simulation studies on the hydrodynamic properties of a self-designed symmetrical three-cylinder buoy. The wave resistance of the buoy was analyzed using different wave conditions, and a full-scale simulation of the buoy was performed using the finite element method and lumped mass method. Experimentally, it was found that the symmetrical three-cylinder buoy stability was less affected by the wave height, but mainly by the wave period. Additionally, the effects of wave height and wave period on mooring tension were also studied, and the results showed that mooring tension was mainly affected by wave period, which was explained by the rate of change of the buoy momentum. Finally, a numerical model was proposed for the interpretation of these experiments. Results from numerical simulations for the trajectory of the buoy and the tension of the mooring cable correlated well with the experimental data.

Factors affecting fisher decisions: The case of the inshore fishery for European sea bass (Dicentrarchus labrax).

Fishery management relies on forecasts of fish abundance over time and space, on scales of months and kilometres. While much research has focussed on the drivers of fish populations, there has been less investigation of the decisions made day-to-day by fishers and their subsequent impact on fishing pressure. Studies that focus on the fisher decisions of smaller vessels may be particularly important due to the prevalence of smaller vessels in many fisheries and their potential vulnerability to bad weather and economic change. Here we outline a methodology with which to identify the factors affecting fisher decisions and success as well as quantifying their effects. We analyse first the decision of when to leave port, and then the success of the fishing trip. Fisher behaviour is here analysed in terms of the decisions taken by fishers in response to bio-physical and socio-economic changes and to illustrate our method, we describe its application to the under 10-meter fleet targeting sea bass in the UK. We document the effects of wave height and show with increasing wave height fewer vessels left port to go fishing. The decision to leave port was only substantially affected by time of high tide at one of the four ports investigated. We measured the success of fishing trips by the landings of sea bass (kg) per metre of vessel length. Fishing success was lower when wave height was greater and when fish price had increased relative to the previous trip. Fuel price was unimportant, but a large proportion of the variation in success was explained by variation between individual vessels, presumably due to variation in skipper ability or technical restrictions due to vessel characteristics. The results are discussed in the context of management of sea bass and other small-scale inshore fisheries.

Large Eddy Simulation of the wave loads on submerged rectangular decks

This study integrates a Large Eddy Simulation model and the Volume of Fluid method to investigate the wave loads on submerged bridge decks. The simulated wave height and surface pressures on the deck are validated by the experimental results of a laboratory flume. The numerical model is utilized to examine the wave/turbulence interaction around a rectangular deck near the water surfaces. In addition, the effects of wave height, scale ratio, submergence ratio, and blockage ratio on the wave loads of the submerged deck are investigated. The simulation results indicate that the drag, lift, and pitching moment on the deck are linearly proportional to the wave height H, and a new normalization scheme is proposed to predict the wave loads of partially and fully submerged decks. On the other hand, the dimensionless force coefficients are functions of submergence depth S, regardless of the scale ratio of the deck model. The maximum force coefficients occur when the submergence ratio S/D = 0∼1.0 and decrease with the increasing submergence ratio, resulting from the wave-induced pressure is largest near the water surfaces. Furthermore, the turbulence induced by the wave breaking and by the bridge deck affects the surface pressure and hydrodynamic force of the partially submerged bridge deck.

Numerical analysis on wave load reduction effect of a solid wall with porous plate by macroscopic CFD approach

The porous structures are widely designed in coastal and ocean engineering to reduce the wave load. A macroscopic CFD approach is established to study the wave interaction with a porous plate placed in front of a solid wall. The established numerical wave tank was firstly validated by the analytical results of a vertical wall, and the macroscopic CFD model was validated by the experimental results of a single vertical porous plate. Then the wave load reduction effect of a solid wall with a vertical porous plate in front is investigated, the influences of porosity and relative gap width are compared, and the effects of wave height are also analyzed. The results demonstrate that the porosity and relative gap width are the main effect factors to the wave force reduction effect, and the wave forces on structure increase almost linearly with the increase of relative wave height, while the wave load reduction coefficient and refection coefficient are not linearly. A porosity of 0.2 and relative gap width of 0.2–0.3 are deemed to be optimal geometry parameters at which the wave load reduction effect is optimal. The total horizontal wave force increases nonlinearly with the increase of wave heights, and the quadratic pressure drop condition is essential when studying the wave force on thin porous structures.

Numerical simulation of deepwater S-lay and J-lay pipeline using vector form intrinsic finite element method

S-lay and J-lay systems are progressively utilized for deepwater pipeline installation. The paper presents a simple and feasible model for the static and dynamic analysis of S-lay and J-lay pipelines. This mechanical model of the laying pipeline is established by the combination of the vector mechanics principle with the numerical technique based upon the vector form intrinsic finite element (VFIFE) method. The internal forces resulted from element deformations and node rotations as well as the external forces due to hydrodynamic loads and the boundary interactions are fully taken into account. The movement governing equation of pipeline particles is solved by the explicit central difference approach using program coding. Two numerical models of a 12-inch pipeline being laid to 1000 m water depth are created in order to illustrate in detail the modeling process of S-laying and J-laying pipeline, respectively, and also verify the feasibility of the VFIFE model with a reasonable accuracy for deepwater pipeline installation. The effects of wave height and sloping seabed on the pipeline responses are identified and the noticeable differences of the pipeline behaviors between the S-lay and J-lay operation are observed. The results offer a significant reference for the installation design of the offshore pipeline.

Hydrodynamic analysis of a seaside quarter-circular breakwater with an array of porous cages using DBEM

ABSTRACT The gravity wave interaction with an array of porous cages in the presence of a seaside submerged quarter-circular porous breakwater (QCPBW) is analyzed within the framework of linearized water wave theory. A quadratic pressure drop is adopted for the wave past the porous structures to capture the effect of wave height on the energy dissipation. The boundary value problem is solved using the iterative Dual Boundary Element Method (DBEM). The numerical code is validated with known results in the literature. One or upto four units of submerged and bottom fixed porous cages are considered. The effect of porosity on QCPBW and porous cages are investigated pragmatically to study the scattering and wave forces. It is found that introducing a single porous cage with 10% porosity at the rear side of a QCPBW with a porosity of 25% can reduce the wave transmission coefficient by about 50% for relative water depth . Increasing the porosity of the single cage from 10% to 40% has a significant reduction on the horizontal and vertical force coefficients on the cage, whereas the change is insignificant on QCPBW. The horizontal wave force is three to four times higher when compared to the vertical wave force for both QCPBW as well as on the porous cage. For a system comprising four units of cages, both the horizontal and vertical wave forces on cage 1, 2, 3, and 4 reduce progressively (cage 2 is at the lee side of cage 1 and so on). The results of the present study can be used for the optimal design of open sea porous systems.

Numerical Study of Heat Transfer Enhancement in Contour Corrugated Channel Using Water and Engine Oil

Improving the design of geometrical parameters of heat exchanger leads to enhance heat transfer and makes it further compacted which in turn increases the efficiency of the thermal process, leading to save operating costs. In the present investigation, thermal and hydraulic performance of laminar flow of the trapezoidal, sinusoidal, and straight counter heat exchanger with water and engine oil was carried out numerically over Reynolds number ranges of 1100-2300 for water and 250 for engine oil. The effect of wave height and wavelength of both trapezoidal and sinusoidal on the thermal properties and hydraulic performance are studied. The numerical study showed that the effect of wave height on the Nusselt number was greater than that of wavelength in both trapezoidal and sinusoidal channels. The study also showed that the trapezoidal channel's influence on Nusselt number was higher than that of the sinusoidal channel and straight channel respectively. Thermal and flow characteristics are explored with the help of the streamwise velocity and isotherms contours for trapezoidal and sinusoidal-corrugated channels. In addition, the success of the heat exchanger design was evaluated by the results of the thermal performance criteria. The results of the thermal performance criteria at all wave heights and wavelength of the corrugated channel were greater than 1, which is indicating that the heat transfer rate is higher than the friction losses. Consequently, the use of corrugated surfaces in Contour heat exchangers can improve heat transfer in many applications.

Iterative dual BEM solution for water wave scattering by breakwaters having perforated thin plates

This study develops an iterative dual BEM (Boundary Element Method) model for water wave scattering by breakwaters having perforated thin plates, which avoids setting artificial sub-domains near the thin plates and thus is very convenient to write general computer codes. In order to directly consider the effect of wave height on the wave energy dissipation by perforated plates, a quadratic (nonlinear) pressure drop condition is imposed on the plates. Then, iterative calculations are conducted to solve the nonlinear boundary condition in the dual BEM model. Also, an analytical method to calculate the integrals of kernel function, which is generated from the hypersingular boundary integral equation in the dual BEM model, is introduced to enhance the calculation efficiency and accuracy. Numerical results show that the iterative calculations in the newly developed dual BEM solution converge rapidly. As examples, wave scattering by several typical breakwaters involving perforated thin plates are solved using the iterative dual BEM model. The corresponding numerical results of the reflection and transmission coefficients are in excellent agreement with the predictions by the analytical solutions. The numerical results also agree reasonably well with experimental data in literature. The present iterative dual BEM model is valuable for analyzing the hydrodynamic performance of breakwaters with perforated thin plates in preliminary engineering design.

Iterative analytical solution for wave reflection by a multi-chamber partially perforated caisson breakwater

This study examines wave reflection by a multi-chamber partially perforated caisson breakwater based on potential theory. A quadratic pressure drop boundary condition at perforated walls is adopted, which can well consider the effect of wave height on the wave dissipation by perforated walls. The matched eigenfunction expansions with iterative calculations are applied to develop an analytical solution for the present problem. The convergences of both the iterative calculations and the series solution itself are confirmed to be satisfactory. The calculation results of the present analytical solution are in excellent agreement with the numerical results of a multi-domain boundary element solution. Also, the predictions by the present solution are in reasonable agreement with experimental data in literature. Major factors that affect the reflection coefficient of the perforated caisson breakwater are examined by calculation examples. The analysis results show that the multi-chamber perforated caisson breakwater has a better wave energy dissipation function (lower reflection coefficient) than the single-chamber type over a broad range of wave frequency and may perform better if the perforated walls have larger porosities. When the porosities of the perforated walls decrease along the incident wave direction, the perforated caisson breakwater can achieve a lower reflection coefficient. The present analytical solution is simple and reliable, and it can be used as an efficient tool for analyzing the hydrodynamic performance of perforated breakwaters in preliminary engineering design.